1. Field of the Invention
The present invention relates to a paper sheet cassette for disposing paper sheets in a stacked state relative to a paper sheet feed roller to feed the stacked paper sheets with the top sheet fed first by the paper sheet feed roller, and especially to a paper sheet cassette comprising a paper sheet containing part for loading and containing paper sheets, and a paper sheet positioning mechanism for determining the position of paper sheets contained in the paper sheet containing part in their width direction which is across the direction of feed of paper sheet by the paper sheet feed roller.
2. Description of Related Art
Paper sheet cassettes of this type and paper sheet feed mechanisms utilizing such paper sheet cassettes are used in various fields. For example, paper sheet cassettes are widely used in image forming devices which are capable of forming images on the paper sheets by feeding paper sheets from a group of paper sheets loaded and contained in a paper sheet cassette by a paper sheet feed roller through an image formation path passing through an image forming portion. Such image forming devices include copying machines, printers, facsimile machines, and multifunctional machines which are the combinations of two or more of these devices.
The reason that the mechanism for positioning paper sheets contained in the paper sheet containing part is employed in such a paper sheet cassette is as follows: Paper sheets are fed by a paper sheet feed roller formed to have a width normally shorter than the width of paper sheets in the direction which is across the direction of feed of paper sheets. In this paper sheet feeding, paper sheets may be skewed due to insufficient positioning of paper sheets. This may adversely affect the following transportation of paper sheets, generate wrinkles in paper sheets, generate noise by the contact between the paper sheets and components associated with transportation of paper sheets, and prevent desired processing on paper sheets. The use of the positioning mechanism is to suppress the generation of such problems by determining the position of the paper sheets so that paper sheets can be fed as straight as possible when fed by the paper sheet feed roller.
Moreover, such a paper sheet positioning mechanism employed sometimes includes a pair of paper sheet side edge positioning members for determining the positions of both side edges of the paper sheets in the width direction of the paper sheets, the pair of paper sheet side edge positioning members being provided on the paper sheet cassette body so as to move toward or away from each other so that the paper sheets can be easily positioned in a predetermined position relative to the paper sheet feed roller, and an interlock mechanism for synchronously moving these pair of paper sheet side edge positioning members toward or away from each other in the width direction of the paper sheets.
Known examples of such an interlock mechanism include those utilizing a rack pinion mechanism.
For example, Japanese Unexamined Patent Publication No. 7-17640 (JP7-17640A) describes a paper sheet positioning mechanism which determines the position of the side edges of paper sheets by moving a pair of paper sheet side edge positioning members toward or away from each other by an interlock mechanism using a′rack pinion mechanism. The publication also describes a mechanism which moves the paper sheets in alignment with a paper passage reference position along with the interlock mechanism in a state that the paper sheets are nipped between the pair of paper sheet side edge positioning members in the width direction of the paper sheets in such a manner.
The positions of the pair of paper sheet side edge positioning members can be easily adjusted according to the paper sheet positioning mechanism which determines the position of paper sheets by nipping the paper sheets in their width direction by adjusting the pair of paper sheet side edge positioning members to move toward or away from each other using the interlock mechanism. However, actually, due to the rattling between the members in the complicated interlock mechanism (for example, in a mechanism using a rack pinion mechanism, rattling caused by backlash in meshing of gears), the position of at least one of the pair of the paper sheet side edge positioning members may be shifted. For this and other reasons, the restriction of the position of the paper sheets by the positioning members may be insufficient and the position of the paper sheets may be shifted.